Consider the phrase a coronation, defined as "a ceremony at which a crown is formally placed on the head of a new king or queen and they officially become king or queen" Oxford Learner's Dictionary. The phrase can also be used figuratively to express a public event in which one ascends to the highest office or echelons of influence in a field. Say what grammatical function the phrase a coronation plays in the sentence below.

When one world leader heard that her friend had been elected prime minister for the $4$th time, she called it a coronation.

Object predicative complement

Object

Subject predictive complement

Subject